Terrazzo grinder



Oct. 18; 1949. H.;J.I POND ETAL TERRAZ Z0 GRINDER 5 Sheecs-Sheet 1 FiledJune 21, 1947 lNVENTOR HAROLD J. POND DANIEL A. ARONES ATTORNEY. S

Oct. 18, 1949. H. J. POND ETAL TERRAZZO GRINDER 5 Sheets-Sheet 2 FiledJune 21, 1947 FIG. 2

36|NVENTOR HAROLD JIPOND DANIEL A. ARONES W 9 AT Tb fiEYs H. J.POND'ETAL Oct. 18', 1949.

TERRAZZO GRINDER Filed June 21'. 1947 5 Sheets-Sheet 3 POND AT TO "Oct.18, 1949. H. J. POND EIAL 2,484,906

TERRAZZO GRINDER Filed June 21, 1947 5 Sheets-Sheet 4 I ll FIG. 4

INVENTOR HAROLD J. POND DANIEL A. ARONES ATTOR YS Filed June 21, 1947III H.'J. POND ET'AL.

vIIIllllllllll lllllllllllll INVENTOR HAROLD J. POND DANIEL A. ARONES gAT??? EYS Patented Oct. 18, 1949 UNITED ES PAT OFFICE.

apolis, Minm, assignors to Advance Machine Company, Minneapolis, Minna,a corporation ofi Mizmesota;

ApplicationJime 21. 1947', Serial No. 7562156 13 Glaims.

Our invention relates to terrazzo grinders and has for anobject toprovide" a. grinder whichcan be conveniently used for grindingverticalsurfaces such as. stair risers, baseboard's, Wainscot borders. and otherterrazzo wall surfaces.

An object of the invention resides inproviding a. grinder which willcover an extended area Without resetting.

A still further object resides. in providinga grinder having, a grindingwheel which. may" be; easily moved toward and from the work' without:resetting. the machine.

Another object of. the. invention resi'desin providing. a grinder whichwill follow. the wall surface. without. the. necessity of setting the.machine accurately with respect to the surface to be ground;

An. object ofthe. invention resides in providing agrinder which may be.used for grinding inclined surfaces or surfaces. out of plumb.

A still further object of. the invention resides in providing. agrinder. inwhich. the grinding wheel when moved toward the, surface tobe ground will be, maintained paraliel tosaid surface.

Other objects of. the. invention. reside in the. novel. combination andarrangement of parts. and. in the details. of construction hereinafterillustrated and/or described;

In the drawings.

Fig. is a front elevational view of a terrazzo. grinder illustrating anembodiment of our. invention.

Fig.. 2. is. a side. view or the structure shown in Fig. 1 with. certainof the. parts in altered position..

Fig. 3. is. aside view similar to. Fig. 2lshowing the parts in still.diflerent. positions.

Fig. 4 is a fragmentary iron-t elevational view of. a. portion at one:of the arms of the invention and showing the method of mounting. the.wheel head, said view being drawn to. a greater scale than Figs- 1, 2.and 3..

Fig. 5' is a. sectional view taken an line. 5.-5 of Fig. 4'.

Fig. 6.- is a longitudinal side elevational sectional view of the jointof the arms. of. the invention and the power transmission mechanism.therein, said. view being drawn tothe. same scale as Fig. 5..

Fig. 7 is a plan sectional view taken on line i of Fig. 6.

Fig. 8 is. a. cross. sectional view taken on. line 8.8 of Fig. 6..

The invention. proper comprises. a base. [0 on which. is mounted a motorll. Motor H has connected to it an arm ['2 which in turn has pivotallyconnected to it by means of. a joint 2. 20 another arm 3i Theamm 153 hasattached to it at its free; end a grinding heart M which. sup.- ports: agrinding wheel: 53 These partsxwilt now be described? in detail.

The base Ml compnisestwom-shaped endframes it and Il which are identicalinconstruction. Onlythe A'- frame I 8 which is: shown in: Fig. 1

will be described in detail'i This frame consists ofparallel framemembers.- IB converging frame members I 9, and a horizontall framemember 2|. connected theretol A cross frame member 22 is weldedtotheparallel frame members: l8. The base H1- further includes two l'ongitudinal frame members 23 whichare welded to the frames l t and I 1 Thebase A is-supported on four wheels 24' and- 25' which extendtransversely of said base and of whichthe wheels: 25- are disposedinwardly of the frame-members P8 of the frame I1. These-wheels aremounted on lugs- 26 which extend downwardly from the framemembenflof'said frame; Bolts 21 extend throughsaid Wheels and are attached tothelugs- 26 and form axles on which said wheels-are rotatably mountedl Thewheels 2'4 are similarly'mourrted on bolts ZB which are attached tolugs- 29*. These lugs are welded to extensions 3 II formed on: the crossframe member 22 of frame [6. This construction brings; the said wheels24 outwardly near the outermost edges of the base I0 By means ofi thisconstruction the entire grinder'may be moved laterally when resting onthe wheels 2'4 and 25 whichpermits ofmoving the grinder along thesurface tobe ground in amanner which will be presently more fullydescribed.

The base- I'U may be moved longitudinally by means of the followingconstruction. Pivotedto thetwo parallel frame members It of" the frame Hare twol'evers 32 These levers have bolts 33 extending through the sameand which are screwed intothe said frame members. The upper ends of thelevers3-2 haveweid'ed to them a handle 34' by means of which the saidlevers may be moved from the fullline position" to" the. dotted lineposition shown in Fig: 2; The lower ends 35 of the-levers- 32havemounted on them wheels 36. Bolts 31'' extend through these wheelsand are screwed into the. ends 35 of the levers 37;" and formaxlesonwhich said wheels rotate. The. ends 35- of said l'evers are angularly'disposed with relerence to the levers. proper so that the. wheels. 36when the said levers are in the position. shown in full lines in Fig. 3"become; raised. above the level' of the surface of which the devicerests. When the handle 3 is moved to its dotted line position its wheels36 are swung downwardly to floor level as shown in Fig. 2. Stops 38 onthe end frame I! limit the swinging movement of the lower ends 35 of thelevers 32. Further swinging movement of the handle 34 causes the wheels24 and 25 to become raised off from the surface on which the device isdisposed and permits of wheeling the device longitudinally by means ofthe wheels 36. A clip 30 holds the lever 32 in its retracted position.

The motor II of the invention is supported by means of a shaft 39, whichis flattened at its ends as designated at 4| in Fig. 1. Pivotallysecured to the ends of the said shaft by means of bolts 42 are two legs43 and 44. These legs are provided with slots 45 which are adapted toreceive bolts 46 extending through the same. 46 are threaded intobrackets 41 welded to the horizontal frame members 2| of the frames I6and If. The bolts 42 extend through off-sets 48 formed on the legs 43whereby the legs 43 and 44 straddle the two end frames I 6 and I1. Bymeans of this construction the shaft 39 may be main tained horizontal asshown in Fig. 2 or the same may be raised at either end and tilted tothe positions shown in full and dotted lines in Fig. 3. By tighteningthe bolts 46 the shaft 39 may be held in any angular adjusted positionwithin the limits afforded by the lengths of the slots 45.

Mounted on the shaft 39 are two bearings 49 which are secured togetherat their lower ends by means'of a flange This flange is bolted by meansof bolts 52 to the motor II. The upper ends of the bearings 49 havesecured to them by means of screws 53 a longitudinally extending bar 54.Mounted between the bearings 49 and secured to the shaft 39 is a sleeve55. This sleeve has bolted to it two blocks 56 which support alongitudinal bar 51. Bars 54 and 51 are substantially the same width andoverlie one another when the arm I2 is in elevated position. A torsioncoil spring 58 encircles the sleeve 55 and has its ends 6| and 62crossed and straddling the two bars 54 and 51. Spring 58 is normallyunder tension so that when the parts are normally at rest the ends 6|and 62 of said spring engage the bars or opposite sides and hold theparts in upright position. When the arm I2 is normally swung from oneside tov the other bar 54 is disengaged from one end of the spring 58and engages the other end to further tension the said spring. This endof the spring then leaves the bar 51. It will thus become readilycomprehended that the weight of the arm and the structure supportedthereby is counterbalanced through the spring 58.

The arm I2 as shown in Figs. 1 and 2 is constructed from two channelmembers 63 which at their lower ends are welded to two cross bars 64.These cross bars are secured to the end bell. 65 of the motor I I bymeans of cap screws 66. The said channel members are attached at theirother ends to a case 67 by means of cap screws 68. These cap screwsextend through slots 69 in the webs of the channel member 63 and arethreaded into the case Bl. The case 61 has two flats II on which thechannel members 63 rest. By means of this construction the case 67 maybe moved toward and from the motor II to adjust the belt and held inadjusted position by means of the cap screws 68.

Within the case 61, as shown in detail in Fig. 6, is rotatably mounted ashaft 12. This shaft is journaled in two ball bearings I3 and 14 whichare mounted in said case. The bearing I3 is received in a bore in thecase 61 and butts The bolts against a shoulder I6 formed in said case. Alook nut TI clamps the said bearing against the shoulder I6. Bearing I4is received in a bore I8 in said case in alignment with the bore 75.This bearing is however free to move within the bore I8. A cover I9closes the bore I8 and when removed gives access to the bearing 74.Mounted on the shaft I2 between the two bearings I3 and I4 is a sheave8| which receives a belt 82 disposed within the interior of the arm I2.This belt passes over another sheave 83 on the rotor shaft 84 of themotor II. By means of this construction the shaft I2 is driven from themotor II. The bearing I5 butts up against a collar 85 of the shaft 82.Sheave 8| butts up against the bearings I3 while a sleeve 89 liesbetween the bearing I4 and said sheave. A nut 81 screwed on the end ofthe shaft 12 holds the parts in proper assembled relation and retainsthe bearing I4 in operative position within the bore I8.

The arm I3 includes a housing 88 having a transverse bore 89 in thesame. In this bore are mounted two ball bearings 9| and 92 which areheld in spaced relation by means of a sleeve 93 disposed between thesame. The bearing 9| butts up against a shoulder 94 formed in thehousing 88 at the end of the bore 89. A nut 95 screwed into the end ofsaid bore holds the two bearings in place therein. The shaft I2 extendsinto the housing 88 and extends through the two bearings 9| and 92.Bearing 9| fits up against a sleeve 96 which fits against a shoulder Ion the shaft I2. A bevel gear 91 butts up against the said bearing andis held in position by means of a key 98 and a lock nut 99 screwed uponthe end of the shaft 12. By means of the housing 88, the case 67, theshaft 12 and the various bearings associated with said shaft the joint20 previously referred to is formed between the two arms I2 and I3permitting the said arms to swing relative to one another about the axisof the shaft 72.

The housing 88 has a branch I02 extending at right angles to the axis ofthe joint 20. This branch has a chamber I03 within the same and in whichthe bevel gear 97 is disposed. The said branch has two bores I04 and I05formed therein which are co-axial and which communicate with the chamberI03. In the bore I04 is mounted a ball bearing I06 while in the boreI05is mounted a ball bearing I01. The bearing I01 butts against ashoulder I08 in the branch I02 of housing 88 and is held in placetherein by means of a sleeve I09 which is threaded to screw into theouter end of the bore I05 and which is held in fixed relation therein bymeans of a lock nut I I I. Journaled in the bearings I 06 and I07 is ashaft II2. This shaft has a shoulder II 3 against which the bearing I0!butts. A bevel gear I I4 extends up to the bearing I01 and is held fromrotation by means of a key I I5. This bevel gear meshes with the bevelgear 9'! on shaft l2. A sleeve I I6 on the shaft I I2 lies between thegear H4 and the bearing I06. A nut II! on the end of the shaft I I2holds the parts in assembled relation on said shaft.

The arm I3 in addition to the housing 88 includes a mounting II9 whichis disposed at the end thereof opposite said housing. This mounting isin the form of a yoke having two side members I2I and I 22 and aconnecting member I 23 therebetween best shown in Fig. 4. A bolt I24connects the two side members I2I and I22 together and holds them inproper spaced relation. The arm I3 further includes three parallel linksI25, I26, and I21. The links I25 and I26 are pivoted to the side membersP24 and I2? of the mounting IFBby'meansTOfIoolts I28 which extendvthrough. said side: members and are screwed into blocks I29 secured to.the ends of said links. The. other ends of the said li'n'kshave attachedto them blocks I 3 f which straddle a; lug I32 formedonthe branch I62"ofhousi'ng'88. Apin' I3? extends through said blocks and boss and"pivotally' connects the ends of the said links to the housing 88' whichforms a portion of" the joint 20. A plate I36 extends. across the blocksIS'I and is secured to said blocks by means of cap screws I34 whichextend through said plate andare threaded into the said? blocks. Bymeans of this construction the ends of the links IZE'I'- and I26 aresecurely tied together: The link I2? is connected to the mounting I I9'and to the housing 88 in much the samemamrer as. the links I and I26.The link IZI is constructed with a block I35 at its upper end whichextends between the two side members I2I and M2 of mounting H9.

A pintle I36 extends through said side members By means oftheconstructi'on forming the arm- I6 I the mounting I'll may be moved inany direction from left toright and vice versa as viewed in Fig. 2 fromthe-dotted line position to-full line position. The arm I3 may beswungabout the axis of the joint 20 and the mounting may be moved toward andfrom the surface of the wall being worked by means of handle I 42. Thishandle is attached toa cross bar I13 extending between the twosidemembers I 2 I and I22 of mounting H9. The weight of the armcounter-balanced by means of a counter-bal anced weight I44 which isslidably mounted on arod I45 and held in positionth'ereon by'means' of aset screw I46. Ihe rod I45 is attached" to a boss I I'I by means of aset screw I 48a Boss In has a flange I49 formed on the same which is secured to the end of thebranch I 02" of case 88 by means of screws I5 Ias-best shown in Fig. 6.

Supported by themounti'ng I I 9 is the grinding head I4 which includes ahousing I 53- best shown in Fig. 5. This housinghas atransverse portionI54 and a longitudinal portion P56. Said housing has a chamber I-5'6-'within the same; In the transverse portion I53 are formed two co-axialbores I5'I and I 58 which receive ball bearings I6I and I62. The ballbearing I-Ii Z- butts up against a shoulder I63 in the: housing I53 andprojects outwardly beyond the end of said ho ns-- ing. E'ncircling saidbearing upon the projecting portion thereof a collar [64 which has ashoulder I65 butting against the outer end of the bearing I62. Thiscollar is secured to: the housing I by means of screws I 66 shown indetail in Fig. 4. Mounted for rotation in the bearings IBI and I62 is ashaft I166. This shaft has an enlarged head I68 iormed= on; the outerend of the same. Encircling the said shaft and dis posed adjacent saidhead is acollar I69 which has a slinger I I I formed onthe outer portionof the same. A spacer I'I 2 also encircles the shaft I66 and buttsagainst the bearing- I 62 mounted on the. shaft I66. Mounted ontheshaf-t- I66 and disposed within the chamber I 56 is: a bevel gear I13This gear iskeyed to the shatit by means of' a key I l 4 and extendsupto the bearing: I62.

.includes a ring armature shaft 815 of motor II.

A sleeve I 15 encircles the said shaft I66" and is disposedbetween theend of the gear I73 and the bearing I6I. A nut I1 6 screwed upon the endof the shaft I-66-hold'stheparts-inassembled relation. Mounted upon theend of the shaft I66 is the grinding wheel: I 5 is cuppedshapcd in form;This wheel is mounted upon the'head I68 of shaft I 66 and butts againstthecollar I69. I66 by means of ascrew IT8= which has a flangedhead Iliiengaging the innermost portion of said wheel. The screw we screws intothreads I B-I formed in the end of the shaft I66 In this manner thewheel I5 is" held mounted upon the end of the'shaft I66;

The-grinding head M is mounted for universalmovement with respect to themounting II-9- by means of auniversal joint indicated in its entirety bythe reference numeral I82. This jointi8-3 which encircles thecollar I64.Screws ass are threaded into the ring and pivots let formed on the endsof the same are received in sockets I66 formed in the collar I 64. Thisconstruction is best shown in Figs. 4 and 5-.

. The two side members IZ'I- and I2? of the mounting Ii't have threadedin them screws I81 which are-similar to the screws I84 and whichhavepivots ltiireceived within'sockets- I69 in the-ring I83. Thesepivots are at right angles to the pivots- !8'5'; By means of thisconstruction the head Ill may be moved about to cause the grindingsurface I9I to conform to the plane of the surface'being ground.

For the purpose of manipulating head I52 aknob- I92 is employed. Thisknob has a boss- I '63 which is received in the outermost end of thebore I5? of housing I53i holds the said knob in place.

Water is furnished to the grinding wheel IT! by means of the followingconstruction. A wa-- ter pump I95 is mounted on the arm I2. This waterpump has a pulley I66 mounted on the drive shaft I96 of the same. A beltI91 passes over this pulley and another pulley I98 on the The pump I95has an inlet tube I98 connected to it which in turn is connected to awater tank 261. Tank 2ilI ismounted on brackets 262 secured to theA-frame Ii. Pump I65 has an outlet tube 203 A set screw I94 connected toit which in turn leads the water to the grinding head I52.

For the purpose of conducting the water to the wheel I5 the knob I92 isconstructed with a water passageway 26E having a nipple 20E screwed intothe same. The tube 263- is con-- nected to the said nipple. The shaftI66 ingrindinghead I52 is formed with a;v bore 206 ex-- tendingcompletely through the same. This bore communicates with a bore 201 inthe screw I18; A tube 1286 is disposed withinv the bores 2:66; and 261.This tube has an enlarged portion 206 at its innermost end which isscrewed intothreads 2II formed in the knob I92. The interior oi the tube266 communicates with the: passageway 264. A felt washer 2I'2encirclesthe tube 2538 and forms a. fluid. tight connection between thenut I16 and the enlarged portion 269 of said' tube. By means or thisvconstruction water is prevented from entering the interior of thehousing I53.

The shaft IE6 is. driven in the. following manner. In the longitudinalportion I55- of housing 153 is formed a: bore 213. In this-bore ismounted two ball bearings 2M and 2115. Bearing 2H3- bears against ashoulder: 216- formed in the: said Said wheel is held in place on shaftportion of the housing. A spacer 2|! holds the two bearings in properrelation within the bore 2I3. A threaded sleeve H8 is screwed into theend of the portion I55 of housing I53 and holds the various parts inposition. Rotatably mounted in the bearings 2Iil and 2H) is a shaft 2l9.This shaft has a shoulder 22l against which the bearing 2M butts. Abevel gear 222 is mounted on the end of the shaft 2I9 and is keyedthereto by means of a key 223. This gear is held in place upon the endof said shaft by means of a nut 224 which is screwed upon said shaft.The gear 222 meshes with the gear H3.

The two shafts 2ft and H2 are connected together by means of a flexibleshaft 225. This shaft has secured to it at its lower end a connector 225which is formed with a fiat 227. Connector 226 is adapted to be receivedwithin a socket 228 in the end of the shaft II2. A slot 229 milled inthe end of the shaft H2 receives a key 23I which engages the flat I2?and holds the shaft 225 from rotation. A collar 232 encircles the shaftH2 and has a set screw 233 in the same which engages the said shaft andclamps the parts in position. By means of this construction the one endof the shaft 225 is connected to the shaft H2 and may slidelongitudinally relative thereto. The other end of the shaft 225 hassecured to it a connector 230 which is connected to the end of the shaft2I9. This connector has a tongue 239 which fits into a slot 24l in theend of the shaft 2I9. A collar 2 12 similar to the collar 232 holds theparts assembled. Encircling the shaft 225 is a flexible tubular case234. This case has attached to the ends of it nipples 225 and 232 whichare secured to the sleeve I59 and the sleeve 2| 8 respectively. A screw23? holds the nipple 235 attached to sleeve I59 while threads 238 on theend of the nipple 23% attach the same to the sleeve 2I8.

The method of using the invention is as follows. The handle 3:3 is firsttilted back to the position shown in dotted lines in Fig. 2 and untilthe lower end 35 of the lever 32 engages the stop 38. Wheels 38 are nowin a position to engage the ground. Further movement of the handle 34 ina downward direction tilts the base I upwardly and raises the wheelsMand 25 above the floor on which the machine is setting. The grinder maynow be convenientl wheeled about to the position where the same is to beused. Upon movement of the handle 34 in the opposite direction supportof the grinder is transferred to wheels 24 and 25 and the wheels 35raised above the floor. When in such position the lever 32 is held inplace by clip 35. The motor II is now energized and the handle I42grasped by one hand and knob I92 by the other. Movement of the arms I2and I3 is now controlled by the handle I42 and the locality of grindingdetermined thereby. By moving the handle I42 toward the surface to beground and by manipulating knob I92 the actual grinding is controlled.

The advantages of the invention are manifest. With our improved terrazzogrinder, grinding may be easily and quickl accomplished. Extended areasmay be ground without moving the entire machine. The machine does nothave to be positioned closely to the surface to be ground. The grinderdoes not have to be accurately aligned with the surface to be ground.The parts of the grinder are counterbalanced in a manner such that thegrinding wheel may be moved about during grinding without undue effort.In the movement of the grinding Wheel toward and from the wall orsurface being ground the wheel travels in a parallel direction. Theangularity of the plane of movement of the grinding wheel may be easilyvaried within considerable limits. The wheel is mounted rigidly on thespindle, with the spindle floating, thu permitting the wheel to run atthe high speeds necessary for maximum efiiciency. This also allows thewheel to be dressed to the desired shape without removing it from thespindle, and permits the us of a round edge wheel for grinding of covebases.

Changes in the specific form of our invention, as herein described, maybe made within the scope of what is claimed without departing from thespirit of our invention.

Having described our invention, what we claim as new and desire toprotect by Letters Patent is:

1. In combination, a support, an arm, a pivotal connection between saidarm and said support, a second arm, a joint between said arms, the axisof said joint being parallel to the axis of said pivotal connection,said joint including a member movable with said second arm, said secondarm including a mounting at the end thereof opposite said member andparallel links pivoted to said member and to said mounting for swingingmovement about parallel axes disposed at right angles to a planecontaining the axis of said joint, a grinding head carried by saidmounting and including a grinding wheel and power transmission means fordriving said grinding wheel.

2. In combination, a support, an arm, a pivotal connection between saidarm and said support, a second arm, a joint between said arms, the axisof said joint being parallel to the axis of said pivotal connection,said joint including a member movable with said second arm, said secondarm including a mounting at the end thereof opposite said member andparallel links pivoted to said member and to said mounting for swingingmovement about parallel axes disposed at right angles to a planecontaining the axis of said joint, a

grinding head including a shaft having its axis parallel to the axis ofsaid joint, a bearing for said shaft carried by said mounting, a shaftcarried by said joint, means for rotating said second shaft, and aflexible shaft extending along said links, said flexible shaft beingdriven from said second shaft and driving said first shaft.

3. In combination, a support, an arm, a pivotal connection between saidarm and said support, a second arm, a joint between said second arm andsaid support, the axis of said joint being parallel to the axis of saidpivotal connection, said joint including a member movable with saidsecond arm, said second arm including a mounting at the end thereofopposite said member and parallel links pivoted to said member and tosaid mounting for swinging movement about parallel axes disposed atright angles to a plane containing the axis of said joint, a grindinhead including a shaft having its axis parallel to the axis of Saidjoint, a bearing for said shaft, a ring encircling .said bearing, pivotmeans between said ring and bearing having its axis at right angles tothe axis of said shaft, other pivot means' between said ring andmounting and having its axis at right angles to a plane containing theaxis of said shaft and said first named pivot means and powertransmission means for driving said first named shaft.

4. In combination, a support, an arm, a pivotal connection between saidarm and said support, a second arm, a joint between said arms, the axisof said joint being parallel to the axis of said pivotal connection,said joint including a member movable with said second arm, said secondarm including a mounting at .the ,end thereof op osite said member andparallel links pivoted ItO said :memberand to said mountinglfor swingingmove- :ment about parallel axes disposed at ri ht angles .to a :planecontaining the raxispf said joint, said links being spacedlongitudinally of the :axis of said joint, a grinding wheel .at the endof said second arm and having its axis parallel to the axis of saidjoint and power transmission means for driving said grinding wheel.

5. In combination, a support, an arm, a pivotal connection between saidarm and said support, a second arm, a joint between said arms the axisof said joint being parallel to the axis of said pivotal connection,said joint including a member movable with said second arm, said secondarm including a mounting at the end thereof opposite said member andthree spaced parallel links, pivots between said links and member andbetween said links and said mounting, the axes of said pivots beingparallel and being disposed at right angles to a plane containing theaxis of said joint, the pivots at each end of two of said links beingco-axial, a grinding head carried by said mounting and including agrinding wheel and power transmission means for driving said grindingwheel.

6. In combination, a support, an arm, a pivotal connection between saidarm and said support, a second arm, a joint between said arms, the axisof said joint being parallel to the axis of said pivotal connection,said joint including a member movable with said second arm, said secondarm including a mounting at the end thereof opposite said member andthree spaced parallel links arranged in the form of a triangle, pivotsbetween said links and member and between said links and said mounting,the axes of said pivots being parallel and being disposed at rightangles to a plane containing the axis of said joint, the pivots at eachend of two of said links being coaxial, a grinding head carried by saidmounting and including a grinding wheel and power transmission means fordriving said grinding wheel.

7. In combination, a support, an arm, a pivotal connection between saidarm and said support, a second arm, a joint between said arms, the axisof said joint being parallel to the axis of said pivotal connection,said joint including a member movable with said second arm, said secondarm including a mounting at the end thereof opposite said member andthree spaced parallel links arranged in the form of a triangle, pivotsbetween said links and member and between said links and said mounting,the axes of said pivots being parallel and being disposed at rightangles to a plane containing the axis of said joint, the pivots at eachend of two of said links being coaxial, a grinding head carriedby saidmounting and including a grinding wheel and a power transmission shaftfor driving said grinding wheel, said shaft being disposed substantiallywithin the confines of said triangle.

8. In combination, a support, comprising two spaced supporting members,a shaft extending across said supporting members, guide means actingbetween each of said supporting members and the shaft for guiding eitherend of the shaft for up and down movement to an extent greater than theother end of the shaft, clamp means for holding the shaft in any of itspositions, a pair of jointed arms, pivot means between said shaft andone of said arms, a grinding wheel .carriedby the other of. said armsand power transmission ,means for driving said grinding wheel.

19.. .In combination, a supporta fixed shaft carried by said support, apair of jointed arms, pivot means betweensaid shaft and one of saidarms, a ,grinding wheel carried by the other of said arms, an abutmenton said shaft, a coil spring encircling said shaft, .the ends .of saidspring engaging said abutment on opposite sides thereof and in a mannerto cause tensioning of-the spring 10. In combination, a support, an arm,a pivotal connection between said arm and said support, a second arm, ajoint between said arms, the axis of said joint being parallel to theaxis of said pivotal connection, said joint including a member movablewith said second arm, said second arm including a mounting at the endthereof opposite said member and parallel links pivoted to said memberand to said mounting for swinging movement about parallel axes disposedat right angles to a plane containing the axis of said joint, a grindinghead, including a shaft having its axis parallel to the axis of saidjoint, a bearing for said shaft, a universal joint between said bearingand mounting and power transmission means for driving said shaft.

11., In combination, a support, an arm, a pivotal connection betweensaid arm and said support, a second arm, a joint between said arms, theaxis of said joint being parallel to the axis of said pivotalconnection, said joint including a member movable with said second arm,said second arm including a mounting at the end thereof opposite saidmember and a link pivoted to said member and to said mounting forswinging movement about parallel axes disposed at right angles to aplane containing the axis of said joint, a grinding head carried by saidmounting and including a grinding wheel and power transmission means fordriving said grinding head.

12. In combination, a support comprising two spaced supporting members,a shaft extending across said supporting members, guide means actingbetween each of said supporting members and the shaft for guiding eitherend of the shaft for up and down movement, clamp means for holding saidshaft in angularly adjusted position and a grinder 'pivotally mounted onsaid shaft and having a grinding wheel disposed remotely from said shaftand adapted to be shifted in position upon swinging of the grinder aboutsaid shaft.

13. In combination, a support, an arm, a pivotal connection between saidarm and said support, a second arm, a joint between said arms, the axisof said joint being parallel to the axis of said pivotal connection,said joint including a member movable with said second arm, said secondarm including a mounting at the end thereof, a grinding wheel carried bysaid mounting and a pivot between the second arm and said member, saidpivot having an axis at right angles to a plane 2,484,906 11 containingthe axes of said pivotal connection and said joint and guiding saidgrinding wheel The following references are of record in the 10 file ofthis patent:

UNITED STATES PATENTS for movement toward and from the surface beingNumber Name Date ground 181,715 Perkins Aug. 29, 1876 HAROLD POND, 5405,961 Kampfe et a1 June 25, 1889 DANIEL A. ARONES. ,8 9 Gall June 19,1917 1,308,933 Cavicchi July 8, 1919 REFERENCES CITED 1,776,110 Dina,Sept. 16, 1930 2,298,228 Pond et a1 Oct. 6, 1942

